19 



of barley on this plot during the fifteen years 1882-96 was 

 485 bushels of corn, and 272 cwts. of straw ; from this we 

 have to deduct 390 bushels of corn, and 225 cwts. of straw, as 

 representing the producing power of the original soil. We 

 have thus 95 bushels of corn, and 47 cwts. of straw, as appa- 

 rently due to the residue of manure remaining in the soil after 

 five small dressings of rich manure. The quantity of manure 

 contributing to the residue was, however, in fact somewhat 

 larger, as, owing to a mistake, the farmyard manure was in 

 one year (1888) put on plot lla, which should have had none, 

 instead of on plot 116, which was intended to be continuously 

 manured. The error has been partly corrected by summing 

 in each case only the manured or unmannred produce ; but 

 the error due to the introduction of a new residue of manure 

 still remains. Beckoning the 95 bushels of barley at 3s. a 

 bushel, its value will be 14. 5s. Od. 



We turn now to the corresponding experiment with wheat. 

 We have here 22*9 bushels as the average produce of five 

 years with farmyard manure, and 20'7, 20-1, and 16*3 

 bushels as the average produce of the first, second, and third 

 five years without manure. In the case of the wheat we are, 

 if possible, in a greater difficulty as to the producing capacity 

 of the land at the beginning of the experiment. The mean 

 produce of the two unmanured plots in the first year was 

 21*5 bushels ; in the first five years, 16 bushels ; and in the 

 first ten years 17-2 bushels of corn, and 17f cwts. of straw. 

 Adopting, as before, the latter figure as the nearest approxi- 

 mation to the truth, we take 18 bushels as representing the 

 original wheat-producing capacity of the land, with 17 cwts. 

 of straw. 



The average produce of plot Ha keeps above the estimated 

 original producing capacity of the land for thirteen years 

 (1882-94), during which time the total produce has amounted 

 to 259-6 bushels of corn, and 234J cwts. of straw. Deducting 

 the 234 bushels and 227^ cwts. corresponding to the original 

 productive capacity of the land, we have in round numbers 

 26 bushels of wheat, and 7 cwts. of straw, as representing the 

 effect of the residue of manure. The wheat at 4s. a bushel 

 will be worth 5. 4s. 



B 2 



